[nchaud]

Hi all

I'm new to this forum and it's good to be here.

I was hoping for some advice about a small project.

I'd like to push a standard 2-Litre car at ~5mph for 10 seconds at a time but all the battery packs/motors that are for EV- conversion seem to be overkill but at the same time, I don't want to buy a motor for a golf cart motor if it won't do the job.

Would be grateful if you could help me figure out which motor to use and also what batteries would be good for it. Please try keep the language simple so a layman can understand it

Thanks!

[nchaud]

Also, it won't interfere with any of the existing car mechanics - will operate almost independently perhaps sticking out at the back driving a dedicated wheel behind the car.

[pedm]

Originally Posted by nchaud

Hi all

I'm new to this forum and it's good to be here.

I was hoping for some advice about a small project.

I'd like to push a standard 2-Litre car at ~5mph for 10 seconds at a time but all the battery packs/motors that are for EV- conversion seem to be overkill but at the same time, I don't want to buy a motor for a golf cart motor if it won't do the job.

Would be grateful if you could help me figure out which motor to use and also what batteries would be good for it. Please try keep the language simple so a layman can understand it

Thanks!

Hi nchaud!

What is the weight of your car?

It is a hybrid conversion project? Or BEV (Battery Electric Vehicle)?

[nchaud]

Originally Posted by pedm

Hi nchaud!

What is the weight of your car?

It is a hybrid conversion project? Or BEV (Battery Electric Vehicle)?

It's about 3500 lbs; it's not a conversion project as such but it would just be an additional motor strapped to the back of the car that has maybe 1 or 2 small wheels that literally push it up to ~5mph

[Ziggythewiz]

Practically any motor designed for an EV could handle that, provided you have the proper gearing, etc. What is the intended purpose?

[dragonsgate]

5mph isn’t much of a power burst. Is this an electric pusher trailer for stop and go traffic trying to save a little gas on acceleration from the lights? If so I would think you need something that will get you up to at least 30mph or more. The car weighs in at 3,500lbs adding another thousand pounds minimum for electric motor and batteries plus trailer weight equals 4,500lbs. Let’s bring it up to 5,000 pounds after you get behind the wheel with a passenger and a bag of groceries. You can find a good forklift motor to handle that. In my opinion you can never have too much power so do not underestimate your needs.

[EVEngineeer]

Lead acid batteries are cheap, but heavy. Lithium batteries are expensive, but lighter weight. What is your price range for your project? That would help everyone figure out what you want. Motors can cost $0-5,000.

[nchaud]

@dragonsgate, actually this is just during heavy traffic - e.g. when there's a highway accident and there's long tailbacks, i just want to use this to push the car up to a max of 5 mph so I was hoping for something much lighter than 1k lbs !

So if we restrict this scenario to a max speed of 5mph with minimal acceleration required, what's the lightest/cheapest motor/battery combination that I could install on my car?

Thanks for the replies !

[Woodsmith]

I can see your plan.

In similar situations I have allowed my car, with the ICE off, to roll if there is a little gradient, or where the law allows and I have been standing beside my car getting some air I just push it a little once in a while.

Unless you have the need to do that very often I am not sure how worthwhile it would be to have a system attached to the car to do that.

If the wheels of the device are on the road then they will need to be able to spin up to the full speed of the car otherwise they will need a method for raising and lowering them to the road surface.
You could look at those trailer movers used at camp and caravan sites, a pair of driven wheels with a tow ball on top. Maybe one of those could be adapted to the task.


There are also motors to drive the wheels, that could work.



I can imagine, if it is a front engine rear wheel drive car then a motor on the propshaft/driveshaft to the rear axle would be an easier proposition.

An Agni95R may be able to spin up to the high speed needed and present little drag and weight when not in use. It would draw high current to move the car at low speed though.

Alternatively a geared motor doing the same job would draw less current moving the car but it would need a freewheel, or sprag clutch, to prevent it from being overspeeded by the propshaft. That would mean no high speed reversing though.

Maybe a motor with a loose belt drive to the tail shaft of the trans or the nose of the diff. The belt tension could be pulled tight with a lever or pneumatic cylinder when drive was needed.

This is all getting a little away from the EV scene though, but still an interesting idea.

Do check the legality issues where you are, just in case there are any issues.



Maybe more ICE car manufacturers should have low power electric drive for maneuvering and parking as a matter of course. I'd like it as an option.

[dragonsgate]

I kind of had a fleeting thought of a friction wheel against the tire like the ones used on bicycles. It is called chicken power. No reflection intended toward this project. It would be hard to get enough pressure between the tire and drive wheel with out a lot of extra time and expense. A small electric powered wheel to push the car could work but there might be some problems to work out. The motor setup will be a lot lighter than the vehicle it is pushing so there might be a traction problem. Add that to the fact that the wheel will most likely be positioned at the rear of the car in the center touching the road where all the oil and gas blow by from other cars is deposited adding to the loss of traction. Anyone who has ever ridden motorcycles for any amount of time will testify that the center of the road can be very slippery. Especially at intersections on a hot day. A hydraulic arm to press down on the electric drive unit transferring some of the vehicle weight might help but again there is the extra expense plus the added weight of the hydraulic unit. Also keep in mind that in order to cut weight you use to small a motor it will burn out in a short time. My contention is if you are going to take the time and money to build something do the job right the first time. The odds are that if you cut corners and build something barely adequate it will not be long before you will wish it was more powerful or faster. There was a PT Cruiser with an electric pusher trailer in this forums garage section but I couldn’t find it.